CNC Machining Question – Tips for Improving Surface Finish

[yovenim]

Hello everyone,

I'm relatively new to CNC machining (https://www.jeeklead.com/sheet-metal-parts/) and have a question regarding surface finishes. I’ve been working on a few parts and, while the dimensions are coming out fine, I’m struggling to achieve a smooth surface finish, especially on aluminum.

I’m using carbide end mills and have tried different feeds and speeds, but the results still seem rough. Could anyone offer some advice on optimizing toolpath strategies, speeds, feeds, or coatings to get a better finish?

I’d appreciate any tips or resources to improve my process.

[Muzzer]

You should be using uncoated inserts or end mills for aluminium. Ideally look for the "honed", "lapped" or "polished" cutters with razor sharp edges (but be careful handling them!). Something like this https://www.cutwel.co.uk/milling-tools/milling-cutters/high-performance-aluminium-milling-cutters/3-flute-square-end-aluminium-milling-cutters/10mm-3-flute-lapped-50-degree-helix-carbide-a-aluminium-end-mill-apfe3-korloy For inserts, the "G" ones with "higher tolerance" are sharp and polished eg CCGT rather CCMT, usually uncoated.

You may find that taking a deeper cut (higher feed rare) actually gives a better finish than a "spring pass". I use coolant or WD40 for best finishes. It's also good to ensure the chips are cleared so they don't get rubbed against the workpiece, using air blast.

[JohnHaine]

What grade of aluminium? Many alloys are horrible to machine. From memory T6061 is good.

[m_c]

Provided you're taking a suitable cut, good finish on Aluminium is mostly about chip clearance.

Either flood coolant, or air (with a bit mist, or even an occasional squirt of light oil such as WD40 to avoid chips sticking to the cutter) to ensure chips are washed/blown away to avoid re-cutting and marking of the cut surface.

[Muzzer]

What grade of aluminium? Many alloys are horrible to machine. From memory T6061 is good.

I assumed most likely 6061 in the US, as he is new to CNC. Equivalent in terms of availability and popularity would be 6082 T6 in the UK - very similar properties and applications.

This is 6082 machined on a 40 yo machine:
https://www.instagram.com/p/ByKcPFYJ_iQ/?img_index=1

It can be done!

[AndyGuid]

This is 6082 machined on a 40 yo machine:
https://www.instagram.com/p/ByKcPFYJ_iQ/?img_index=1


That finish looks amazing!